The immune system is the body's major defense mechanism against infections and neoplasm. The vertebrate immune system is divided into two functional parts; humoral immunity and cell-mediated immunity. Humoral immunity represents biomolecular components of the immume system which are produced by cells and secreted into the body's circulatory system. Cell-mediated immunity is characterized by the direct action of various leukocytic cells upon targeted foreign substances that are present in the body. Concerted action of these interrelated systems affords protection from a wide variety of infectious diseases and neoplasms.
Under normal circumstances, the presence of foreign substances in the body provokes a response from the cells which synthesize and secrete components of the humoral system. Specifically, B lymphocytes synthesize specific proteins, that is antibodies, which bind to selected sites on the foreign organism. After the antibodies bind to sites on the foreign organism or transformed cells, the foreign cells or viruses may then be destroyed through action of the cell-mediated immune system, or by the action of other humoral fractions, or directly inactivated by the antibody molecules themselves.
Ordinarily, antibody molecules are not directed at the host's own or "self" agents. In certain individuals, however, the immune system mistakenly mounts an immune attack against itself, much in the same manner that it would for a foreign invader. Inflammation, damage, or outright tissue destruction often results from these autoimmune responses. The results of such autoimmune conflicts are dramatic. Symptoms therefore diseases include the inability to utilize sugar (type I diabetes), destruction of joints (rheumatoid arthritis), kidney destruction (systemic lupus erythematosus, glomerulonephritis, and like diseases), and destruction of the vascular system (vasculitis). Each autoimmune disorder leads to prolonged suffering together with early mortality.
Many autoimmune diseases are accompanied by persistently high concentrations of blood-borne autoimmune complexes. These autoimmune complexes usually contain a variety of anti-antibodies, rheumatoid factors, and other species which form extended immune complexes together with the target antigens. Much of the damage produced by the autoimmune diseases may be traced to the efforts of the cell-mediated immune system to eliminate such extended autoimmune complexes, wherever they may be found. Control of these diseases has proven difficult in the past, partly because the detection methods employed inadequately discriminated between levels of extended immune complexes of normal and disease states.
Many different techniques have been attempted for obtaining accurate, rapid and inexpensive methods of immune complex detection. Many techniques are quite ingenious, but no method has proven to be totally adequate. Examples of the limitations in prior methods of detection follow.
Firstly, the Raji cell assay depends upon the presence of cell surface receptors for immune complexes, and these receptors only appear at precise times in the growth of the culture.
Secondly, complement fractions or monoclonal antibodies directed against them are often employed in radioimmuno- or enzyme-linked immunosorbent assays. Unfortunately, both complement and selected monoclonal antibody used to immobilize complement have been shown to be labile proteins. This instability, particularly in the complement fraction, leads to impaired test sensitivity, specificity and reproducibility. Consequently, methods which depend upon complement immobilization either by direct or antibody-mediated adherence, are inadequate for clinical testing because of this labile property of the complement and selected antibody.
Thirdly, immunoglobulin class and size limit the utility of complement-based assays. Neither Raji cell nor complement-based assays can detect all antibody classes and subclasses in the immune complex. These assays are restricted to IgM, IgG.sub.1, IgG.sub.2. Furthermore, they are restricted to complexes with molecular mass greater than 1,000,000 Daltons. These two criteria represent serious limitations because many harmful complexes are significantly smaller than 1,000,000 Daltons.
Lastly, liquid physicochemical techniques utilizing precipitation with substances like polyethylene glycol, dextran, or Staphylococcus aureas protein A are considered unwidely because of the difficulties inherent in handling small and often flocculent precipitates. Adventitious binding of immunologically unrelated immunoglobulins to the precipitate further degrades the performance of such tests. Together, these difficulties seriously impair the utility of physicochemical methods of immune complex measurement.
To overcome such limitations, numerous tests must be run, thereby increasing the cost to the patient. As a consequence, the various tests are not normally performed with sufficient frequency to monitor the progress of a patient's disease properly. Development of an inexpensive, selective, effective means of adhering the immune complex to a solid support is essential to overcome these problems.
It is therefore an objective of the present invention to provide compositions, methods and articles for the selective adsorption or affixing of immune complexes which will be effective for detecting a wide variety of classes and subclasses of immune complexes.
It is a further objective of this invention to overcome the aforementioned selectivity, stability, and handling disadvantages inherent in other methods of immune complex adsorption to solid surfaces for the purposes of assay, removal of immune complexes from serum, and the like.
It is yet a further objective of this invention to provide novel, highly adaptable, and readily utilizable means for the detection of components of said complexes after affixation to a support, and further to use such techniques for the purposes of clinical detection, removal, concentration, or any other purpose or utility associated with human or veterinary medical applications.